Free volumetric flow rate converter. Convert gallons per minute (GPM) to liters per minute, m³/h, liters per second, cubic feet per minute (CFM), and more — for plumbing, pumps, pools, aquariums, and HVAC. Instant results with strong validation.
GPM • L/min • m³/h • L/s • CFM
GPM here is US gallons per minute (1 gal = 3.78541 L) — the standard for US plumbing, pumps and pools.
Sized for plumbing, well pumps, pool turnover, aquariums, and HVAC airflow (CFM) in one tool.
All conversions run in your browser — no server, no account, nothing sent anywhere.
Volumetric flow rate measures how much volume passes a point per unit time. In the US, water flow is usually given in gallons per minute (GPM), while the rest of the world uses liters per minute (L/min) or cubic meters per hour (m³/h). Airflow for HVAC and fans is measured in cubic feet per minute (CFM). Because a US gallon equals 3.78541 liters, the most common conversion — GPM to L/min — is simply multiplying by 3.78541.
Key conversions: 1 GPM = 3.785 L/min = 0.0631 L/s = 0.227 m³/h. 1 L/s = 15.85 GPM = 60 L/min = 3.6 m³/h. 1 m³/h = 4.403 GPM = 16.67 L/min. 1 CFM = 1.699 m³/h = 28.32 L/min. Note that US GPM differs from UK/Imperial GPM, because a UK gallon (4.54609 L) is about 20% larger than a US gallon — this converter uses US gallons throughout.
Real-world reference points: a typical kitchen faucet flows 1.5–2.2 GPM, a shower head 1.8–2.5 GPM (US efficiency standard caps shower heads at 2.5 GPM), a garden hose 9–17 GPM, and a residential well pump 8–12 GPM. Pool pumps move 40–80 GPM. For HVAC, a bathroom exhaust fan is around 50–110 CFM, while a whole-house furnace blower moves 1,000–2,000 CFM.
Kitchen faucet: 1.5–2.2 GPM. Shower: 1.8–2.5 GPM. Bathtub fill: 4–8 GPM. Garden hose: 9–17 GPM. Dishwasher: ~1 GPM. Washing machine: ~3–5 GPM during fill.
Pool pump: 40–80 GPM. Well pump: 8–12 GPM. To turn over a 20,000-gallon pool in 8 hours you need ~42 GPM. Aquarium filter: typically 4–10× tank volume per hour.
Bathroom fan: 50–110 CFM. Range hood: 200–400 CFM. Furnace blower: 1,000–2,000 CFM. Rule of thumb: ~400 CFM per ton of AC cooling. 1 CFM = 1.699 m³/h.
1 GPM = 3.785 L/min. 1 L/s = 15.85 GPM. 1 m³/h = 4.403 GPM. 1 CFS = 448.8 GPM. US gallon = 3.78541 L; UK gallon = 4.546 L (this tool uses US).
Volumetric flow rate is volume per unit time, and it inherits every ambiguity of volume units — including the US versus imperial gallon, which differ by 20%. A pump rated at 25 GPM moves noticeably different quantities depending on which gallon the manufacturer meant. Flow relates to velocity through the pipe's cross-sectional area, and because area scales with the square of diameter, small changes in pipe size have large effects: doubling the diameter quadruples the area and, at the same velocity, quadruples the flow. This is why undersized pipework throttles a system far more than intuition suggests.
Q = v × Alitres per second = value × factor_from1 US GPM = 0.0630902 L/s · 1 m³/h = 0.277778 L/s · 1 CFM = 0.471947 L/swhere:
Assumptions: Volumetric flow, not mass flow. For gases, volume depends strongly on pressure and temperature, so gas flows are often quoted at "standard" conditions (SCFM) which must be stated to be useful.
Convert a US pump rating and find the resulting fluid velocity.
Result25 GPM = 1.577 L/s = 5.68 m³/h (0.80 m/s in 50 mm pipe)
Velocity matters more than flow for pipe sizing: above roughly 2.5 m/s water systems become audible and erosion accelerates, while below 0.5 m/s sediment settles out. Pressure loss rises with roughly the square of velocity, so halving pipe diameter costs far more than it saves.